Influence of elevated temperature on bond performance of basalt FRP bars with steel fiber-reinforced concrete

Abdulaziz, Mohammed; Abbas, Husain; Elsanadedy, Hussein; Abadel, Aref; Almusallam, Tarek; Al-Salloum, Yousef

doi:10.2478/msp-2025-0050

Figures & Tables

Figure 1

(a) Steel fibers; (b) BFRP rebars used in the study; and (c) BFRP rebar's surface profile.

Beam-end test specimen details (all dimensions are in mm).

Temperature–time variation followed in heating and cooling.

Failure modes of rebars embedded in PC and FRC.

Comparison of bond strength of rebars embedded in PC and FRC after exposure to different temperatures: (a) steel vs BFRP bars in PC; (b) steel vs BFRP bars in FRC; (c) steel bars in PC vs FRC; and (d) BFRP bars in PC vs FRC.

Bond stress–slip curves of steel and BFRP rebars embedded in PC and FRC after exposure to different temperatures: (a) steel bar embedded in PC; (b) BFRP bar embedded in PC; (c) steel bar embedded in FRC; and (d) BFRP bar embedded in FRC.

Modified mBPE model vs experimental bond stress–slip curves of rebars embedded in PC at ambient and elevated temperatures: (a, c, and e) steel rebars exposed to ambient temperature, 100°C, and 200°C; and (b, d, and f) BFRP rebars exposed to ambient temperature, 100°C, and 200°C.

Modified mBPE model vs experimental bond stress–slip curves of rebars embedded in FRC at ambient and elevated temperatures: (a, c, and e) steel rebars exposed to ambient temperature, 100°C, and 200°C; and (b, d, and f) BFRP rebars exposed to ambient temperature, 100°C, and 200°C.

Comparison of predicted and experimental bond strength for: (a) steel rebars embedded in PC and (b) steel rebars embedded in FRC.

Comparison of predicted with experimental bond strength for: (a) BFRP rebars embedded in PC and (b) BFRP rebars embedded in FRC.

Test matrix_

S. No.	Specimen ID	Volume fraction of steel fibers	Type of test rebar	Diameter of rebar (mm)	Exposure temperature	No. of test specimens
1	PCSB-A	0	Steel	12	Ambient temperature	2
2	PCSB-100	0	Steel	12	100°C	2
3	PCSB-200	0	Steel	12	200°C	2
4	FRCSB-A	1%	Steel	12	Ambient temperature	2
5	FRCSB-100	1%	Steel	12	100°C	2
6	FRCSB-200	1%	Steel	12	200°C	2
7	PCBB-A	0	BFRP	12	Ambient temperature	2
8	PCBB-100	0	BFRP	12	100°C	2
9	PCBB-200	0	BFRP	12	200°C	2
10	FRCBB-A	1%	BFRP	12	Ambient temperature	2
11	FRCBB-100	1%	BFRP	12	100°C	2
12	FRCBB-200	1%	BFRP	12	200°C	2
					Total = 24

Equations of bond model parameters as a function of exposure temperature_

Embedded in PC*	Embedded in FRC*
	Steel rebars
α = 0.0005 T + 0.867 \alpha =0.0005T+0.867 (R ² = 0.99)	α = 0.001 T + 0.525 \alpha =0.001T+0.525 (R ² = 0.99)
ρ = 0.0001 T 2 − 0.0282 T + 2.114 \rho =0.0001{T}^{2}-0.0282T+2.114 (R ² = 1.00)	ρ = 9 × 10 − 6 T 2 − 0.0009 T + 0.21 \rho =9\times {10}^{-6}{T}^{2}-0.0009T+0.21 (R ² = 1.00)
s max = 0.0031 T + 2.844 {s}_{\max }=0.0031T+2.844 (R ² = 0.98)	s max = 0.0077 T + 1.167 {s}_{\max }=0.0077T+1.167 (R ² = 0.86)
r = 0.0006 T + 0.1885 r=0.0006T+0.1885 (R ² = 0.99)	r = 0.0006 T + 0.1885 r=0.0006T+0.1885 (R ² = 0.99)
	BFRP rebars
α = 0.0009 T + 0.652 \alpha =0.0009T+0.652 (R ² = 0.93)	α = 0.0011 T + 0.652 \alpha =0.0011T+0.652 (R ² = 0.89)
ρ = 0.0024 T + 0.0762 \rho =0.0024T+0.0762 (R ² = 0.99)	ρ = 2 × 10 − 5 T + 0.102 \rho =2\times {10}^{-5}T+0.102 (R ² = 1.00)
s max = 0.005 T + 1.978 {s}_{\max }=0.005T+1.978 (R ² = 0.79)	s max = 0.0015 T + 1.796 {s}_{\max }=0.0015T+1.796 (R ² = 0.95)
r = 0.0017 T + 0.244 r=0.0017T+0.244 (R ² = 0.88)	r = 0.0017 T + 0.244 r=0.0017T+0.244 (R ² = 0.88)

Codes and researchers’ models for bond strength of steel rebars embedded in concrete*_

Code/Researcher	Model for ambient temperature	Model for elevated temperature
ACI 408R-03 [26]	τ max , 20 = 20 f c ' d b {\tau }_{\max ,20}=20\frac{\sqrt{{f}_{\text{c}}^{\text{'}}}}{{d}_{\text{b}}}	NA
CEB-FIP Model Code [34]	τ max , 20 = 2 f c ' {\tau }_{\max ,20}=2\sqrt{{f}_{\text{c}}^{\text{'}}}	NA
CEB-FIP Model Code [35]	τ max , 20 = 2.5 f c ' {\tau }_{\max ,20}=2.5\sqrt{{f}_{\text{c}}^{\text{'}}}	NA
Huang [36]	τ max , 20 = 2.5 f c ' {\tau }_{\max ,20}=2.5\sqrt{{f}_{\text{c}}^{\text{'}}}	τ max , T = 2.5 f c ' for 20 ≤ T ≤ 400 C ∘ f c ' 0.4 for 400 < T ≤ 800 C ∘ 0 for T > 800 C ∘ {\tau }_{\max ,T}=\left\{\begin{array}{c}2.5\sqrt{{f}_{\text{c}}^{\text{'}}}\text{for}20\le T\le \text{400}{}^{\circ }\text{C}\\ {f}_{\text{c}}^{\text{'}}0.4\text{for}400\lt T\le \text{800}{}^{\circ }\text{C}\\ 0\text{for}T\gt \text{800}{}^{\circ }\text{C}\end{array}\right.
Lublóy and György [37]	τ max , 20 = 2 f c ' {\tau }_{\max ,20}=2\sqrt{{f}_{\text{c}}^{\text{'}}}	τ max , T = 2 f c ' 1.0 − 0.22 360 ( T − 20 ) for 20 ≤ T ≤ 380 C ∘ 2 f c ' 0.78 − 0.75 270 ( T − 380 ) for 380 < T ≤ 650 C ∘ 0.06 f c ' for T > 650 C ∘ {\tau }_{\max ,T}=\left\{\begin{array}{c}2\sqrt{{f}_{\text{c}}^{\text{'}}}\left(1.0-\frac{0.22}{360}(T-20)\right)\text{for}20\le T\le \text{380}{}^{\circ }\text{C}\\ 2\sqrt{{f}_{\text{c}}^{\text{'}}}\left(0.78-\frac{0.75}{270}(T-380)\right)\text{for}380\lt T\le \text{650}{}^{\circ }\text{C}\\ 0.06\sqrt{{f}_{\text{c}}^{\text{'}}}\text{for}T\gt \text{650}{}^{\circ }\text{C}\end{array}\right.

Prediction of bond strength of BFRP rebars using codes and researchers’ models_

Specimen ID	Bond strength model
	ACI 440.1R-15 [8]		CAN/CSA-S6-14 [11]		JSCE [38]		Model (1) – El-Gamal [39]		Model (2) – El-Gamal [39]		Özkal et al. [40]
	τ max , TH {\tau }_{\max ,\text{TH}} (MPa)	τ max , TH τ max , EXP \frac{{\tau }_{\max ,\text{TH}}}{{\tau }_{\max ,\text{EXP}}}	τ max , TH {\tau }_{\max ,\text{TH}} (MPa)	τ max , TH τ max , EXP \frac{{\tau }_{\max ,\text{TH}}}{{\tau }_{\max ,\text{EXP}}}	τ max , TH {\tau }_{\max ,\text{TH}} (MPa)	τ max , TH τ max , EXP \frac{{\tau }_{\max ,\text{TH}}}{{\tau }_{\max ,\text{EXP}}}	τ max , TH {\tau }_{\max ,\text{TH}} (MPa)	τ max , TH τ max , EXP \frac{{\tau }_{\max ,\text{TH}}}{{\tau }_{\max ,\text{EXP}}}	τ max , TH {\tau }_{\max ,\text{TH}} (MPa)	τ max , TH τ max , EXP \frac{{\tau }_{\max ,\text{TH}}}{{\tau }_{\max ,\text{EXP}}}	τ max , TH {\tau }_{\max ,\text{TH}} (MPa)	τ max , TH τ max , EXP \frac{{\tau }_{\max ,\text{TH}}}{{\tau }_{\max ,\text{EXP}}}
PCBB-A	13.50	0.81	8.40	0.51	6.47	0.39	10.93	0.66	16.20	0.98	13.50	0.81
PCBB-100	NA	—	NA	—	NA	—	8.85	0.48	14.12	0.77	11.68	0.63
PCBB-200	NA	—	NA	—	NA	—	6.25	0.35	11.53	0.64	10.02	0.56
FRCBB-A	14.13	0.97	8.80	0.61	6.81	0.47	11.43	0.79	16.96	1.17	14.13	0.97
FRCBB-100	NA	—	NA	—	NA	—	9.36	0.52	14.88	0.83	12.22	0.68
FRCBB-200	NA	—	NA	—	NA	—	6.76	0.40	12.28	0.72	10.49	0.62

Prediction of bond strength of steel rebars using codes and researchers’ models*_

Specimen ID	Bond strength model
	ACI 408R-03 [26]		CEB-FIP model code [34]		CEB-FIP model code [35]		Huang [36]		Lublóy & György [37]
	τ max , TH {\tau }_{\max ,\text{TH}} (MPa)	τ max , TH τ max , EXP \frac{{\tau }_{\max ,\text{TH}}}{{\tau }_{\max ,\text{EXP}}}	τ max , TH {\tau }_{\max ,\text{TH}} (MPa)	τ max , TH τ max , EXP \frac{{\tau }_{\max ,\text{TH}}}{{\tau }_{\max ,\text{EXP}}}	τ max , TH {\tau }_{\max ,\text{TH}} (MPa)	τ max , TH τ max , EXP \frac{{\tau }_{\max ,\text{TH}}}{{\tau }_{\max ,\text{EXP}}}	τ max , TH {\tau }_{\max ,\text{TH}} (MPa)	τ max , TH τ max , EXP \frac{{\tau }_{\max ,\text{TH}}}{{\tau }_{\max ,\text{EXP}}}	τ max , TH {\tau }_{\max ,\text{TH}} (MPa)	τ max , TH τ max , EXP \frac{{\tau }_{\max ,\text{TH}}}{{\tau }_{\max ,\text{EXP}}}
PCSB-A	10.80	0.56	12.96	0.67	16.20	0.84	12.96	0.67	16.20	0.84
PCSB-100	NA	—	NA	—	NA	—	12.33	0.65	16.20	0.86
PCSB-200	NA	—	NA	—	NA	—	11.54	0.80	16.20	1.13
FRCSB-A	11.3	0.63	13.56	0.76	16.96	0.95	13.56	0.76	16.96	0.95
FRCSB-100	NA	—	NA	—	NA	—	12.90	0.74	16.96	0.97
FRCSB-200	NA	—	NA	—	NA	—	12.07	0.83	16.96	1.17

mBPE model parameters obtained by curve fitting_

Concrete type	Rebar type	Exposure temperature	Model parameters
Concrete type	Rebar type	Exposure temperature	α \alpha	ρ \rho	r r	s _max
PC	Steel rebar	Ambient temperature	0.88	1.500	0.15	2.895
		100°C	0.91	0.750	0.12	3.200
		200°C	0.96	2.300	0.55	3.445
	BFRP rebar	Ambient temperature	0.69	0.124	0.300	1.955
		100°C	0.72	0.340	0.100	2.735
		200°C	0.85	0.550	0.18	2.865
FRC	Steel rebar	Ambient temperature	0.55	0.190	0.20	1.540
		100°C	0.62	0.205	0.25	1.615
		200°C	0.72	0.380	0.30	2.835
	BFRP rebar	Ambient temperature	0.70	0.100	0.25	1.630
		100°C	0.72	0.110	0.48	2.295
		200°C	0.88	0.105	0.56	1.935

Compressive and splitting tensile strengths of concrete at ambient and elevated temperature_

Concrete type	Compressive strength (MPa)		Splitting tensile strength (MPa)
Concrete type	Ambient temperature	200 °C	Ambient temperature	200 °C
PC	42.0 ± 2.8	41.4 ± 3.2	3.8 ± 0.2	3.7 ± 0.3
FRC	46.0 ± 3.1	45.2 ± 3.3	6.0± 0.5	5.8 ± 0.6

Summary of study results_

Specimen ID	Peak force (kN)	Average bond strength (MPa)	Slip at peak load (mm)	Residual bond stress (MPa)	Failure mode*
PCSB-A	43.9 ± 2.40	19.3 ± 1.05	2.895 ± 0.12	2.9 ± 0.14	P & S
PCSB-100	42.8 ± 2.91	18.9 ± 1.29	3.200 ± 0.13	2.3 ± 0.16	P & S
PCSB-200	32.5 ± 1.84	14.4 ± 0.81	3.445 ± 0.15	7.9 ± 0.54	P & S
FRCSB-A	40.4 ± 2.51	17.9 ± 1.11	1.540 ± 0.1	3.6 ± 0.28	P
FRCSB-100	39.3 ± 3.10	17.4 ± 1.37	1.615 ± 0.12	4.4 ± 0.28	P
FRCSB-200	32.9 ± 2.37	14.5 ± 1.05	2.835 ± 0.24	4.4 ± 0.35	P
PCBB-A	37.5 ± 1.58	16.6 ± 0.7	1.955 ± 0.09	5.0 ± 0.28	P & S
PCBB-100	41.7 ± 2.42	18.4 ± 1.07	2.735 ± 0.15	1.8 ± 0.13	P & S
PCBB-200	40.7 ± 2.46	18.0 ± 1.09	2.865 ± 0.19	3.2 ± 0.28	P & S
FRCBB-A	32.9 ± 2.13	14.5 ± 0.94	1.630 ± 0.08	3.6 ± 0.25	P
FRCBB-100	40.7 ± 3.34	18.0 ± 1.48	2.295 ± 0.12	8.7 ± 0.64	P
FRCBB-200	38.5 ± 3.02	17.0 ± 1.34	1.935 ± 0.13	9.5 ± 0.78	P & S

Codes and researchers’ models for bond strength of BFRP bars embedded in concrete*_

Code/Researcher	Model for ambient temperature	Model for elevated temperature
ACI 440.1R-15 [8]	τ max , 20 = 0.083 f c ' 4.0 + 0.3 C d b + 100 d b ℓ e {\tau }_{\max ,20}=0.083\sqrt{{f}_{c}^{\text{'}}}\left(\phantom{\rule[-0.75em]{}{0ex}},4.0+0.3\frac{C}{{d}_{b}}+100\frac{{d}_{b}}{{\ell }_{e}}\right)	NA
CAN/CSA-S6-14 [11]	τ max , 20 = 0.4 f c ' d c s 0.45 π d b k 1 k 4 {\tau }_{\max ,20}=\frac{0.4\sqrt{{f}_{c}^{\text{'}}}{d}_{cs}}{0.45\pi {d}_{b}{k}_{1}{k}_{4}}	NA
JSCE [38]	τ max , 20 = 0.318 + 0.795 c d b 3.2 f c ' − 53.2 f fu {\tau }_{\max ,20}=\frac{0.318+0.795\frac{c}{{d}_{\text{b}}}}{\frac{3.2}{\sqrt{{f}_{\text{c}}^{\text{'}}}}-\frac{53.2}{{f}_{\text{fu}}}}	NA
Model (1) – El-Gamal [39]	τ max , 20 = 20.23 f c ' d b {\tau }_{\max ,20}=20.23\frac{\sqrt{{f}_{\text{c}}^{\text{'}}}}{{d}_{\text{b}}}	τ max , T = 20.23 f c ' d b − 0.015 Δ T t {\tau }_{\max ,T}=20.23\frac{\sqrt{{f}_{\text{c}}^{\text{'}}}}{{d}_{\text{b}}}-0.015\Delta T\sqrt{t}
Model (2) – El-Gamal [39]	τ max , 20 = 2.5 f c ' {\tau }_{\max ,20}=2.5\sqrt{{f}_{\text{c}}^{\text{'}}}	τ max , T = 2.5 f c ' − 0.015 Δ T t {\tau }_{\max ,T}=2.5\sqrt{{f}_{\text{c}}^{\text{'}}}-0.015\Delta T\sqrt{t}
Özkal et al. [40]	τ max , 20 = 0.083 f c ' 4.0 + 0.3 C d b + 100 d b ℓ e {\tau }_{\max ,20}=0.083\sqrt{{f}_{\text{c}}^{\text{'}}}\left(\phantom{\rule[-0.75em]{}{0ex}},4.0+0.3\frac{C}{{d}_{\text{b}}}+100\frac{{d}_{\text{b}}}{{\ell }_{\text{e}}}\right)	τ max , T = γ f η f f ( T ) 20 ≤ T ≤ 600 C ∘ γ f = τ max , FRP , 20 τ max , steel, 20 η f = 1473 − T 1,450 f ( T ) = 0.981 τ max , steel , 20 1 − T 1,450 τ max , steel, 20 = 20 f c ' d b τ max , FRP , 20 = 0.083 f c ' 4.0 + 0.3 C d b + 100 d b ℓ e \begin{array}{c}{\tau }_{\max ,T}={\gamma }_{\text{f}}{\eta }_{\text{f}}f(T)\text{20}\le T\le 600{}^{\circ }\text{C}\\ {\gamma }_{f}=\frac{{\tau }_{\max ,\text{FRP},20}}{{\tau }_{\max ,\text{steel,}20}}\\ {\eta }_{f}=\frac{1473-T}{\mathrm{1,450}}\\ f(T)=0.981{\tau }_{\max ,\text{steel},20}\left(\phantom{\rule[-0.75em]{}{0ex}},1-\frac{T}{\mathrm{1,450}}\right)\\ {\tau }_{\max ,\text{steel,}20}=20\frac{\sqrt{{f}_{\text{c}}^{\text{'}}}}{{d}_{\text{b}}}\\ {\tau }_{\max ,\text{FRP},20}=0.083\sqrt{{f}_{\text{c}}^{\text{'}}}\left(\phantom{\rule[-0.75em]{}{0ex}},4.0+0.3\frac{C}{{d}_{\text{b}}}+100\frac{{d}_{\text{b}}}{{\ell }_{\text{e}}}\right)\end{array}

Influence of elevated temperature on bond performance of basalt FRP bars with steel fiber-reinforced concrete

Figures & Tables

Figure 1

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Figure 10

Figure 11

Test matrix_

Equations of bond model parameters as a function of exposure temperature_

Codes and researchers’ models for bond strength of steel rebars embedded in concrete*_

Prediction of bond strength of BFRP rebars using codes and researchers’ models_

Prediction of bond strength of steel rebars using codes and researchers’ models*_

mBPE model parameters obtained by curve fitting_

Compressive and splitting tensile strengths of concrete at ambient and elevated temperature_

Summary of study results_

Codes and researchers’ models for bond strength of BFRP bars embedded in concrete*_

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